a) Field of the Invention
The invention is directed to a suspension of a valve plate of a vacuum valve at a valve rod. The invention is further directed to a vacuum valve with a valve body having a valve opening with a valve seat, a valve plate which is suspended at a valve rod, and an actuation device by means of which the valve plate is movable from its open position initially into a position in which it is located opposite to the valve opening, but is lifted from the valve seat, and then can be pressed against the valve seat.
b) Description of the Related Art
Vacuum valves of the plate valve type in which the valve opening is closed by a valve plate which is pressed against the valve seat surrounding the valve opening are known in many different constructional forms.
A first conventional embodiment form of such plate valves is the slide valve. In slide valves, in order to close the valve, the valve plate is initially displaced by an actuation device linearly in one direction transverse to the sealing surface until it reaches a position opposite to the valve opening, but in which it is lifted from the valve seat. Subsequently, a movement is carried out vertical to the sealing surface and in the direction of the longitudinal axis of the valve opening, so that the valve plate is pressed against the valve seat. This two-step movement process is required so that the seal of elastic material, for example, Viton, is not exposed to shearing stress, which would lead to impermissible wear. The second step of the closing movement is achieved in different ways in slide valves of this kind, for example, by means of lifting mechanisms, rolling bodies which are guided in wedge-shaped gaps between the valve plate and a supporting plate, tilting elements, and so on. In order to prevent bending of the valve rod in the second movement step (movement vertical to the sealing surface and valve opening), a counter-plate is usually provided which is simultaneously moved against a wall located opposite to the valve seat. Such slide valves are known, for example, from U.S. Pat. No. 4,560,141 A, DE 3209217 C2, DE 3224387 C2, and U.S. Pat. No. 3,185,435 A.
In a special type of plate valve or slide valve, the second movement step, that is, the movement of the valve plate against the valve seat is carried out by a movement which is directed essentially vertical to the sealing surface in that the valve rod is swiveled about a pivot point. This pivot point can be formed by pins or rollers arranged laterally at the valve rod and which are guided in guide grooves. The valve rod is accordingly constructed in the manner of a lever which is initially linearly displaced and then tilted. The construction must be correspondingly sturdy to prevent deformation of the valve rod when the valve plate is pressed against the valve seat. Examples of valve constructions of this kind are shown in U.S. Pat. Nos. 5,415,376 A, 5,641,149 A, 6,045,117 A, 5,934,646 A, 5,755,255 A, 6,082,706 A, and 6,095,180 A.
In another type of plate valve, there is no linear displacement of the valve plate in the first movement step, but rather a swiveling along a circular arc in order to move the valve plate into the position located opposite from the valve opening. For this purpose, the valve rod is suspended at a shaft by its end located opposite to the valve plate so as to be swivelable about an axis vertical to the valve surface. The second step of the closing movement of the valve plate in the direction of the valve seat is carried out by means of a linear displacement of this shaft. It is also already known to suspend the valve plate at this shaft by means of a swivel bearing, wherein a spring device pretensions the valve plate in the position in which it is lifted from the valve seat. The second step of the closing movement is carried out in that the shaft is displaced linearly in a direction which runs parallel to the central axis of the valve opening, but which faces away from the valve opening. A kind of bulge in the valve rod which is arranged in the middle area of the valve rod is accordingly pressed against a wall of the valve body and rolls along this wall, so that the valve plate is displaced against the valve opening. The valve plate is connected with the valve rod via a rotating or swiveling bearing.
It is the primary object of the invention to provide a suspension of a valve plate of a vacuum valve at a valve rod which improves the contact of the valve plate at the valve seat. It is another object of the invention to provide a suspension of a valve plate at a valve rod so as to simplify the valve construction and economize on material. Another object of the invention is to provide a vacuum valve of the type mentioned above with a suspension of the valve plate at the valve rod in such a way that the contact of the valve plate at the valve seat is improved, the seal is protected and the construction of the valve is simplified and is economical with respect to material.
According to the invention, these and other objects proceeding from the description are met by a suspension of the valve plate at the valve rod which comprises a bearing block of rubber-elastic material with first and second side surfaces, one of which side surfaces is fastened to the valve rod or to a plate which is rigidly connected with the latter, and the other side surface is fastened to the valve plate or to a plate which is rigidly connected with the latter, wherein an inelastic force transmission part is embedded in the rubber-elastic material of the bearing block and extends at oppositely located points or along oppositely located lines up to the side surfaces of the bearing block.
The rubber-elastic material of the bearing block makes it possible for the valve plate to tilt relative to the valve rod, wherein the points or lines of the force transmission part which extend up to the surfaces of the side surfaces of the bearing block form swivel points or swivel lines for the swiveling of the valve plate relative to the valve rod. Further, a small longitudinal movement of the valve plate relative to the valve rod is also made possible as will be explained in more detail in the following. The inelastic force transmission part which is embedded in the rubber-elastic material of the bearing block also serves to transmit the contact pressing force of the valve rod to the valve plate in order to ensure long-term strength of the suspension when used over a longer period with a plurality of opening and closing processes of the valve. When opening the valve, the elastic material of the bearing block also causes the valve plate to return to the zero position.
Further, the suspension according to the invention has the advantage that when the valve plate is swiveled relative to the valve rod or when the valve plate is moved longitudinally relative to the valve rod there is hardly any release of particles which would otherwise impair the functionality of the chambers for sensitive processes with respect to impurities (for example, when handling wafers with highly pure surfaces). The occurrence of such particles cannot be prevented in principle during the movement of two parts relative to one another, in this case, during the movement of the surfaces contacting the force transmission element relative to the latter. However, in the suspension according to the invention, these particles are enclosed by the material of the bearing block and can accordingly not be released into the vacuum.
The various features and developments according to the invention are indicated in the claims.
Further advantages and details of the invention are explained more fully in the following with reference to the embodiment examples which are shown in the drawing, wherein further details of the invention are also indicated.